The present invention relates to irrigation equipment, and more particularly, to sprinklers of the type that use internal turbines to rotate a nozzle to distribute water over turf or other landscaping.
Many regions of the world have inadequate rainfall to support lawns, gardens and other landscaping during dry periods. Sprinklers are commonly used to distribute water over such landscaping in commercial and residential environments. The water is supplied under pressure from municipal sources, wells and storage reservoirs. So called xe2x80x9chose endxe2x80x9d sprinklers were at one time in widespread use. As the name implies, they are devices connected to the end of a garden hose for ejecting water in a spray pattern over a lawn or garden. Fixed spray head sprinklers which are connected to an underground network of pipes have come into widespread use for watering smaller areas. Impact drive sprinklers have also been used to water landscaping over larger areas starting decades ago. They are mounted to the top of a fixed vertical pipe or riser and have a spring biased arm that oscillates about a vertical axis as a result of one end intercepting a stream of water from a nozzle. The resultant torque causes the nozzle to gradually move over an adjustable arc and a reversing mechanism causes the nozzle to retrace the arc in a repetitive manner. Rotor type sprinklers have largely supplanted impact drive sprinklers, particularly on golf courses and playing fields, because they are quieter, more reliable and distribute a much more precise amount of precipitation more uniformly over a given sector size.
A rotor type sprinkler typically employs an extensible riser which pops up out of a fixed outer housing when water pressure is applied. The riser has a nozzle in a rotating head mounted at the upper end of the riser. The riser incorporates a turbine which drives the rotating head via a gear train reduction, reversing mechanism and arc adjustment mechanism. The turbine is typically located in the lower part of the riser and rotates about a vertical axis at relatively high spend.
Golf courses typically utilize so called xe2x80x9cvalve-in-headxe2x80x9d rotors which operate under relatively high water pressures, e.g. seventy PSI and higher. They incorporate ON/OFF diaphragm valves in their lower ends that can be opened and closed under electrical or pneumatic control. In regions that experience freezing conditions in the Winter, it is necessary to winterize a sprinkler system. This involves removing all of the water in the system to prevent breakages otherwise due to the expansion of water as it freezes. A common way of removing the water is to pressurize the supply lines that lead to the various rotors with air. This can last as long as two to eight hours. This causes the turbines to spin at rotational rates which are too high, often damaging the turbine bearings and/or turbine shaft. The rotor normally moves one complete resolution in about three minutes. With only purging air flowing through the rotor, this cycle time can be reduced to fifteen seconds. The water in a rotor typically functions as a lubricating medium for the turbine drive shaft, and its absence can lead to melted plastic bearings. Grit next to an over-spinning turbine drive shaft can eventually sever the shaft. When such irrigation systems are re-activated in the Spring, the supply lines are refilled with high pressure water. This pushes out any air in the system through the rotors, once again subjecting their turbines and related nozzle drive components to potential damage. Surge conditions resulting from a mixture of high pressure water and air can also damage the turbine bearings and related nozzle drive components of a rotor type sprinkler.
U.S. Pat. No. 4,815,662 of Edwin J. Hunter discloses a rotary stream sprinkler in which a stream of water strikes an inverted, vaned conical distributor head. A damping device is connected to the distributor head for controlling the rotational velocity thereof. The damping device includes a rotor inside and oil-filled stator housing. This design places a constant drag on the rotation of the distributor head and is incapable of selectively applying the drag only if the fluid entering the sprinkler is air or a mixture of water and air.
U.S. Pat. No. 5,375,768 of Edwin J Hunter discloses a sprinkler including a multiple range variable speed turbine. A throttling device controllably directs a first portion of water to the turbine, and a pressure responsive valve controllably diverts a second portion of the water around the turbine in proportion to the pressure thereof for maintaining the speed of the turbine substantially constant. Again, this device is not designed to detect air or a mixture of water and air and to perform the diversion if the fluid entering the sprinkler is not substantially entirely water.
It is therefore the primary object of the present invention to provide a rotor type sprinkler designed to prevent over-spinning of its turbine when subjected to pressurized air or a mixture of pressurized water and air.
According to the present invention, a sprinkler includes a riser for receiving a pressurized fluid and a nozzle that is mounted at an upper end of the riser for rotation about an axis. A turbine is mounted for rotation inside the riser. A drive mechanism connects the turbine to the nozzle so that rotation of the turbine by the pressurized fluid rotates the nozzle. The sprinkler includes mechanisms for preventing over-spinning of the turbine when the pressurized fluid is air or a mixture of air and water. Damage due to over-spinning of the turbine is thereby avoided. In one version of the sprinkler, the over-spinning prevention mechanism applies a brake force to the turbine. In another version of the sprinkler, the over-spinning prevention mechanism re-directs air or a mixture of water and air around the turbine.